Ultrasound imaging has become increasingly popular because of its ability to obtain images of internal body organs through non-invasive or minimally invasive techniques. Therefore, it is an ideal choice for many preliminary examinations, such as obstetrical or cardiology exams, and screenings for certain types of growth irregularities, such as tumors, without requiring substantial incisions.
Ultrasound imaging systems typically operate by transmitting ultrasound signals through a transducer which contains an array of piezoelectric elements capable of converting an applied voltage into mechanical motion and vice versa. In this way ultrasound acoustic signals can be transmitted into a medium where reflections, caused by impedance mismatches at acoustic interfaces within the medium, are received back at the transducer. Received acoustic signals are then converted back to electrical signals which are sent to a signal processor where, among other things, they are amplified and processed to construct visual image that can be displayed. The signal processor and display are generally a combine unit whereas the ultrasound transducer is typically in the form of a hand-held probe.
Transducer probes are manufactured in many different forms, including small diameter invasive tools such as catheters and endo-cavity probes. Non-invasive probes are usually palm size and hand-held, and are used, for example, in prenatal examinations of a fetus and in diagnosing cardiac health.
The manufacture of complex devices such hand-held transducer probes typically involves the integration of multiple components. FIG. 1 is a perspective view of a typical prior art hand-held transducer probe, generally referred by reference number 100. Transducer 100 is comprised of machined, cast or injection molded components including a nosepiece assembly 112, comprised of a plastic nosepiece and interior acoustic components, an acoustic lens or window 114, a plastic case handle 116 designed to be grasped by the user's hand, a flexible cable 118 for transmitting electrical signals to and from a signal processing unit (not shown), and a strain relief 120 for preventing cable 118 from fraying. Grip features 122, such as raised ribs or depressions are also shown. An alternative construction of case handles 116 comprises attaching together two clam shell-shaped or other part break-up case handle components.
Ultrasound technicians use transducer probes 100 for extended periods of time and utilize a variety of hand-hold positions. Technicians have experienced fatigue while holding onto the transducer probes 100, especially when wearing gloves and employing coupling gel. The variety of hand sizes and grip configurations of technicians cause difficulty in working with current transducer probes 100 for long periods of time. Once formed, rigid case handles 116 are relatively slippery and hard, thereby compounding grip problems for technicians if used alone. Many methods of improving the grip of case handles have been attempted with limited success. For example, increasing the friction of the case handle 116 has been tried by adding textured surfaces and/or raised ribs 122 and depressions to the case handle 116, but these adjustments did not improve the grip problems to the desired degree.
The grip features 122 of the prior art provide some improvement to a more secure grip of the probe 100 than when there are no grip features 122. Operator fatigue is an undesirable outcome of extensive use. Reducing operator fatigue is a favored usability quality.
Traditional transducer case handles 116 are made from the polysulfone, polycarbonate, or rigid polyurethane families of plastics. The case handle 116 material is chosen for structural strength, impact resistance and chemical resistance. The plastic case handle 116 materials employed in the prior art have a relatively low coefficient of friction and can feel slippery in the operator's hand, especially when gloves and gel are used by the ultrasonographer. These polymerics have good engineering properties, but are also hard and non-compliant. When the probe 100 feels slippery, technicians tend to hold the transducer 100 more tightly. The combination of a tight grip on a hard surface for an extended period of time exacerbates the problem of operator fatigue.
Recently, "ergonomic" transducer case handles 116 have been designed to reduce operator fatigue and discomfort by fitting to the human hand for the variety of applications and positions dictated to acquire ultrasound images. An example of such a handle is shown by Barnes et al. in U.S. Pat. No. 4,582,066.
U.S. Pat. No. 5,505,205, by Solomon et al., discloses elastomeric polymers employed as a transmissive interface over the acoustic window (see, for example, window 114 of FIG. 1) for conducting ultrasound energy from the transducer to a patient's body. The polymeric materials of Solomon are chosen so that the sound speed in the polymeric materials approximately matches the speed of sound and the impedance of the soft tissues in the human body. This is a highly specialized and expensive polymeric material. Moreover, this entire probe is not sealed and therefore only the nose piece is immersible in fluid to disinfect the probe. The probe cannot be fully immersed.
U.S. Pat. No. 5,381,795, by Nordgren et al., discloses a transducer design that uses a rubber-like encapsulated boot around the acoustic window of the probe to insulate the patient from the electrical connections to the transducer crystal and to permit immersion of the boot in a sterilizing liquid. The Nordgren patent teaches that the lower portion of the case closes around the boot.
Copending U.S. application Ser. No. 08/646,155 (abandoned), by Van Creveld et al., discloses a transducer probe design wherein a transducer acoustic assembly encapsulated with rubber-like acoustic lens or window material such as room temperature vulcanizing silicone rubber (RTV). The RTV compound forms both the lens and the case handle. There is no use of an underlying hard case handle material. While this copending application partially addresses the grip and comfort problems discussed above, it has certain aesthetic and functional disadvantages. The aesthetic disadvantage of complete encapsulation may limit the perceived functional goal of being a finely engineered medical device. The RTV or similar purpose material is chosen based on its ability to function as a transmissive interface for conducting ultrasound energy from the transducer to a patient's body. It is designed for low acoustic attenuation and for impedance that matches the impedance of body tissue. Preferred RTV compounds require accurate formulas to meet these and other non-acoustic needs, and therefore, are expensive and have relatively low tear strengths. This RTV-type material is also applied over a transducer probe assembly in a relatively expensive and time-consuming casting and curing process. Furthermore, complete coverage of the probe surface with RTV elastomer impedes smooth manipulation of the probe when placed against the patient's skin to obtain an ultrasound reading.
Accordingly, there exists a need for a transducer probe that allows the operator to grip the transducer more comfortably and securely than previously possible while also facilitating desired smooth manipulation in rotating and translating probe position while the probe is placed against a patient's skin.
There also exists a need for a transducer probe that is liquid tight for complete immersion disinfecting fluid.
There also exists a need for a transducer probe grip surface design which can be personalized in size, shape and color design.
There also exists a need for a transducer probe design which can be manufactured at lower cost and with robust, high tear strength materials which will survive mechanical abuse.